1. Field of the Invention
The present invention is directed to intraocular lenses (IOLs) that define an optical power that is adjustable following implantation. More particularly, the IOL is adapted for use in cataract patients that require an adjustment in the optical power of the lens post-implantation.
2. Description of the Related Art
Cataracts are a major cause of blindness in the world and the most prevalent ocular disease. Visual disability from cataracts accounts for more than 8 million physician office visits per year. When the disability from cataracts affects or alters an individual's activities of daily living, surgical lens removal with intraocular lens implantation is the preferred method of treating the functional limitations. In the United States, about 2.5 million cataract surgical procedures are performed annually, making it the most common surgery for Americans over the age of 65. About 97 percent of cataract surgery patients receive intraocular lens implants, with the annual costs for cataract surgery and associated care in the United States being upwards of $4 billion.
A cataract is any opacity of a patient's lens, whether it is a localized opacity or a diffuse general loss of transparency. To be clinically significant, however, the cataract must cause a significant reduction in visual acuity or a functional impairment. A cataract occurs as a result of aging or secondary to hereditary factors, trauma, inflammation, metabolic or nutritional disorders, or radiation. Age-related cataract conditions are the most common.
In treating a cataract, the surgeon removes material from the lens capsule and replaces it with an intraocular lens (IOL) implant. The typical IOL provides a selected focal length that allows the patient to have fairly good distance vision. Since the lens can no longer accommodate, the patient typically need glasses for reading.
The surgeon selects the power of the IOL based on analysis of refractive characteristics of the patient's eye prior to the surgery. In a significant number or cases, after the patient's eye has healed from the cataract surgery, there is a refractive error that could not be predicted. There remain substantial difficulties in calculating the proper power of an IOL for any particular patient. To solve any unpredicted refractive errors following IOL implantation, the ophthalmologist can perform a repeat surgery to replace the IOL—or the patient can live with the refractive error that may require prescription eyeglasses for both near and distant vision. What is needed is an IOL that carries means for adjusting its power post-implantation, as well as for treating astigmatisms.